Intake manifolds for internal combustion engines used in automotive applications have typically been manufactured with metallic materials such as cast iron or alloys of aluminum or magnesium having high temperature durability. Weight and manufacturing concerns have given way to the use of thermoplastics on engines. When used in the construction of intakes, weight is significantly reduced and, in many cases, performance is improved as a result of precise control of interior finish and reduced heat transfer to the inlet air.
Incorporation of recirculated exhaust gas (EGR) to intake manifolds manufactured using thermoplastics is a principle design challenge as exhaust gas temperatures must be maintained at temperatures which often exceed design specifications of the thermoplastic material. With metallic manifolds, EGR conduits may be attached directly to the manifold EGR inlet with little concern. Thermoplastic manifolds require cooling of the exhaust gas or insulation between the EGR inlet and the supply conduit.
Additional automotive design criteria require that under hood components utilize a minimum of space due to the proliferation of components packaged therein. Traditional EGR supply systems include a steel tube assembly, encased in an insulating material to protect surrounding componentry. The tube includes an attachment flange at each end for communication with the exhaust gas supply and the intake air manifold. The assembly is routed through the engine compartment and is, by nature, expensive and bulky.
Additionally, engine intake manifolds may have precise intake pressure parameters which, necessarily, are to be maintained in order to avoid performance and durability penalties. In such instances, intake manifolds may incorporate pressure valves in order to maintain intake pressures within desirable ranges. The pressure valves add to the complexity and cost of the intake manifolds.